A senior defense analyst at Rand Corporation says North Korea could conduct a fourth nuclear test using weapons with much greater explosive power.
 
Analyst Bruce Bennett of the U.S. think tank told Yonhap News on Monday that North Korea could try to create a weapon with a boosted yield. He said such a weapon would involve a certain element of fusion as opposed to pure fission that would take the explosive power to about 20 kilotons or maybe up into the 30 to 50 kiloton range.

North Korea experts have recently speculated that Pyongyang could attempt a fourth nuclear test in the atmosphere. Bennett said an atmospheric test is possible, but it would enrage the Chinese government because of fallout from the bomb in the sky.